Building Functional Nanodevices with Vesicle-Templated Porous Polymer Nanocapsules

Abstract

Conspectus Vesicle-templated nanocapsules offer a unique combination of properties enabled by robust shells with single-nanometer thickness containing programmed uniform pores capable of fast and selective mass transfer. These capsules emerged as a versatile platform for creating functional devices, such as nanoreactors, nanosensors, and containers for the delivery of drugs and imaging agents. Nanocapsules are synthesized by a directed assembly method using self-assembled bilayers of vesicles as temporary scaffolds. In this approach, hydrophobic building blocks are loaded into the hydrophobic interior of vesicles formed from lipids or surfactants. Pore-forming templates are codissolved with the monomers and cross-linkers in the interior of the bilayer. The polymerization forms a cross-linked shell with embedded pore-forming templates. Removal of the surfactant scaffold and pore-forming templates leads to free-standing nanocapsules with shells containing uniform imprinted nanopores. Development of reliable and scalable synthetic methods for the modular construction of capsules with tunable properties has opened the opportunity to pursue practical applications of nanocapsules. In this Account, we discuss how unique properties of vesicle-templated nanocapsules translate into the creation of functional nanodevices. Specifically, we focus the conversation on applications aiming at the delivery of drugs and imaging agents, creation of fast-acting and selective nanoreactors, and fabrication of nanoprobes for sensing and imaging. We present a brief overview of the synthesis of nanocapsules with an emphasis on recent developments leading to robust synthetic methods including the synthesis under physiological conditions and creation of biodegradable nanocapsules. We then highlight unique properties of nanocapsules essential for practical applications, such as precise control of pore size and chemical environment, selective permeability, and ultrafast transport through the pores. We discuss new motifs for catch and release of small molecules with porous nanocapsules based on controlling the microenvironment inside the nanocapsules, regulating the charge on the orifice of nanopores in the shells, and reversible synergistic action of host and guest forming a supramolecular complex in nanocapsules. We demonstrate successful creation of fast-acting and selective nanoreactors by encapsulation of diverse homogeneous and nanoparticle catalysts. Due to unhindered flow of substrates and products through the nanopores, encapsulation did not compromise catalytic efficiency and, in fact, improved the stability of entrapped catalysts. We present robust nanoprobes based on nanocapsules with entrapped sensing agents and show how the encapsulation resulted in selective measurements with fast response times in challenging conditions, such as small volumes and complex mixtures. Throughout this Account, we highlight the advantages of encapsulation and discuss the opportunities for future design of nanodevices.

Bilayer‐Templated Two‐Dimensional RAFT Polymerization for Directed Assembly of Polymer Nanostructures

“…In the past, we and others used the free‐radical polymerization of hydrophobic monomers in the hydrophobic interior of different assemblies of amphiphilic molecules to produce nanocapsules, nanodisks, and nanorods . Nanocapsules, having an average diameter programmed between 40 to 400 nm with narrow size distribution and the ability to entrap and retain molecules and nanoparticles, showed utility in diverse applications, such as nanoreactors, nanosensors, and containers for the delivery of drugs and imaging agents .…”

Avidin Localizations in pH-Responsive Polymersomes for Probing the Docking of Biotinylated (Macro)molecules in the Membrane and Lumen

“…Some of them focus on the creation of vesicle-templated porous nanocapsules with a precise control of pore size and selective permeability. [24][25][26][27] Another attractive and useful alternative is the membrane integration of biomacromolecules (enzymes, protein pores, protein channels, etc.) into the polymersomes.…”

Bilayer‐Templated Two‐Dimensional RAFT Polymerization for Directed Assembly of Polymer Nanostructures

“…The uniform single‐nanometer thickness of the shells was confirmed by small‐angle neutron scattering . Controlled permeability of nanocapsules was crucial in the assembly of hierarchical nanostructures and functional nanodevices . These recent studies highlighted the need for integrating synthetic techniques capable of greater structural control in the directed assembly of polymer nanomaterials as well as for better understanding of the polymerization within organized self‐assembled scaffolds.…”

“…In the past, we and others used the free‐radical polymerization of hydrophobic monomers in the hydrophobic interior of different assemblies of amphiphilic molecules to produce nanocapsules, nanodisks, and nanorods . Nanocapsules, having an average diameter programmed between 40 to 400 nm with narrow size distribution and the ability to entrap and retain molecules and nanoparticles, showed utility in diverse applications, such as nanoreactors, nanosensors, and containers for the delivery of drugs and imaging agents .…”